In the BBS world of the late 1980s and early 1990s, one could easily find digital art that celebrated consumer brands, like the image of a Coke can seen here. In fact, I'd say brand art was a particularly distinctive genre of early computer art.
If I had to explain why brand art was so common, I'd first speculate that when people needed something to test out their imaging equipment with — say, a new scanner or a video digitizer card — an advertisement or product package was always at hand to be a guinea pig.
More importantly, consumer brands also inspire loyalty that consumers identify with personally. Think Doritos and Mountain Dew. Fans of those products like to spread their love of them as a cultural identifier, and the same was true in the 1980s and 1990s online space.